Linux: RedHat packaging updates for RHEL6

Linux: RedHat packaging updates for RHEL6

Update our bundled spec file and related tools so they can be used
to build OpenAFS on the RHEL6 beta.

- Make kmodtool recognise el6 as having "modern" kernel naming
  conventions
- Replace %{PACKAGE_VERSION} (which seems to have disappeared)
  with the standard %{version} macro

Thanks to billings and phalenor on IRC for their testing efforts.

Change-Id: I6538af56f365952b98c2dcbafb1c043435449e63
Reviewed-on: http://gerrit.openafs.org/1806
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>